Highly purified aspartate aminotransferase of pig hearts will be prepared and used in collaborative work with Arthur Arnone at the University of Iowa for determination of the 3-dimensional structure at high resolution. We will measure polarized 1ight spectrum on crystals of the free enzyme and of various enzyme-substrate complexes and complexes with inhibitors. Various other spectroscopic techniques will also be applied. The aim will be to obtain a step-by-step picture of the structure at each stage of reaction and to understand at each stage the electronic interactions of the coenzyme with groups in the protein. Chemical studies of glutamate decarboxylase of E. coli will be continued. The unusual product of the reaction of serine-O-sulfate with this enzyme will be characterized as will a new protein factor required for the reaction. Some experiments with brain glutamate decarboxylase will be initiated. A series of crystalline Schiff bases of pyridoxal phosphate and related substances will be prepared and studied by x-ray diffraction and microspectrophotometry. Studies of equilibria in solution of pyridoxal phosphate with amino acids and polyamines will also be conducted. Studies of various analogs of pyridoxal phosphate will be continued. The analogs will be incorporated into enzymes including crystalline aspartate aminotransferase. Some new analogs will be synthesized. Analysis of absorption spectra of aspartate aminotransferase and glutamate decarboxylase using lognormal distribution curves will be developed further. Particular attention will be paid to the visualization of changes in vibrational structure accompanying chemical reactions.